Slitting chisel



Nov. 22, 1960 w, VQNHQFF, JR., E1- AL 2,960,767

SLITTING CHISEL Filed March 30, 1960 United fates Patent i assets? Patented Nov.`V 22, i960 2,960,767 sLrTrNo cinsL William Ynlolf; Jr.; and arl Patterson, Jr., Aurora, lll., assigno'rs 'to Thor Powe Tool Company, Aurora, Ill., a corporation of Delaware shea Mer. su, 1960, ser. ne. iasss s clarifie; (el. 30u91) This invention relates to an improved chisel and more particularly to' an imprved slitting chisel for use with an air hammer orthe like. l v

A slitting chisel is upsedfoi' inakiiig" a lengthwise or ax'ial cut in a cylindrieal or tubularlm'ember. However, in certain instanties it is neessary to slit and remove' a cylindrical metal section which is mounted, either internally or externally, o'ii another cylindrical member which must not be damaged 'r distig'ureddurin`gy the slitting operation. For exa'iple,l in the removal and replacementof automotive exhaust pipes and riuiiiers it is frequently desirable to save either ,the mullier or the exhaust pipe. In orde to do this, a straight cu't is' mede at the appropria'te point through oi adjacent the onnection between the exhaust pipe am die' maaier' stub, and there-after e surting chisel is utilized to' retrieve the innerV or outer annular fragment from the part being saved.` Heretofofe, during the slitting operation there li'as been a serious danger of scoring,` gouging, or" otherwise damaging the part intended to be' saved, andial chisels or tools have been proposed inv o'rdei" t6' minimize this dii'culty.v However, the'pl"eeautiorls: osis'ay to avoid' suoli daiiia'g will Vary dependent upon whether-l an inside out of an outside cut r "I tice to provide two 0r ting chisels in order to meet these varyents".

Aceordirig'lfy, the geiieil object* of'A the" present invention is to providea' novel a'n'd impr ved slitting chisel' which eliminates the' need' fr' separate-f feels fer-1 differenty typesererrairigf-epereuensa Y A Y A further object er are invent-ies is te' prevale never dual functioning slittingE chisel adapted' toi rliak eitli'erv4 inside o''outsi'de cuts duringv thief r'erii'oval of an annular fragment from a concentric main portion.

Another` objectlofthernvjention isito provide-a novel and improvedslitting chisel especially adapted for use in the removal and replacement of automotive exhaust therf objects `andadvantages of thef invention` will` bel come appaiierlt from the subsequent detailed taken iconjunctionwiththe acinpanying drawing; wherein:

Fig. 1 is a small scale elevational view showing the manner in which the slitting chisel of the present invention is used in making an outside cut for removing an exhaust pipe fragment from the exterior of a muiiier stub;

Fig. 2. is a view similar to Fig. 1 but showing use of the chisel in making an inside cut for removing a muiier stub fragment from the interior of yan exhaust pipe;

Fig. 3 is an enlarged cross-sectional view of the outside cutting operation shown in Fig. 1;

Fig. 4 is an enlarged cross-sectional view of the inside cutting operation shown in Fig. 2;

Fig. 5 is a large scale plan view of t-he working end Y of the slitting chisel;

Fig. 6 is a side elevational view of the slitting chisel; Fig. 7 is an end view as seen along the line 7-7 of Fig. 6;

Figs. 8-13 are cross-sectional views taken along the lines 8-8, 9-9, 1010, 11-11, 12-12, and 13-13, respectively, of Fig. 6;

Fig. 4 is an enlarged fragmentary, longitudinal sectional view taken along the line 14-14 of Fig. 7; and

Fig.` 15 is a view similar to Fig. 14 but taken along the line 15-15 of Fig. 7.

Referring first to Figs. 5-15, the chisel 20 comprises an elongated metal body having a shank 21 with a circumferential flange or retaining lug 22 at one end for cooperation with a suitable holder or tool and a cutting portion 23 at its opposite end. The shank 21 has an intermediate offset bend 24 to facilitate use of the chisel.

The cutting portion 23 of the chisel comprises a pair of elongated blade portions 26 and 27 disposed in angularly related fashion so as to form a channel 28 therebetween which is generally V-shaped in cross-section in a plane transverse to the longitudinal axis of the chisel, as best seen in Figs. 8-13. The generallyl V-shaped channel extends along the longitudinal axis of the tool in substantially symmetrical relation with respect thereto, as best seen in Fig. 5. The outermost ends of the blade portions 26-27 are smoothly tapered along their longitudinal edges and substantially in the planes of the respective blade portions, as best seen in Fig. 5, and the inner tapered edges of the blade portions converge at a juncture disposed axially inwardly from the tips vof the blade portions so `as to provide a rearwardly recessed crotch 29 at theY apex ofthe V-shaped channel. The edge of the crotch 29 is sharpened, as at 31,- to provide a cutting action s hereinafter described. y The depth o f the V-sllap'ed channel 28 decreases rearwardly from the crotch 29 by reason of a' rearwardly increasing thickness of the meta-l along the apex of Vthe channel thereby providing a v tapered channel bottom 32, as best seen in Fig. 6 and as portion 26prfer'a`bly being sharpened from both sides thereof as seen at 33 in Fig. 14, `and the blade portion 27 preferably being sharpened only from the inside thereof as seen at 34'v in' Fig. y15. l

The' primary feature of the inventionI resides in the utility o f the chisel for making' either an inside oran outside longitudinalslitting cut `between a pair of concentricarlly rel-'ated tubular members.` To facilitate this dual functioning, the blade portion 26 has its outermost lateral surface formed withl a generally convex or outwardly' bulged curvature and the blade portion 27 has its corresponding outermost lateral surface formed with a generally concave orv inwardly depressed curvature, as will' be clear from Figs. 8 to 131 `The opposite curvatures orcontours' of then respective blade portions 2`6`Hand4 27 facilitateiaxial' feeding of the tool; against either the inner or outer curved periphery of a tubular member, as will now be described.

Referring particularly to Figs. l to 4, an air hammer 40 of a well known type is shown having an operating trigger 41 and a coiled retainer spring 42 cooperable with the flange 22 for holding Ithe chisel 20 in the tool. The chisel is illustrated in connection with the removal and replacement of an automative muffler and exhaust pipe.

In Fig. l a muffler 43 is shown having connecting stubs 44 for connecting the muilier to an exhaust pipe 46 and another exhaust pipe shovm fragmentarily at 47. A transverse or straight cut has been made through the muffler stub-exhaust pipe connection at a point beyond the end of the stub 44 so that the mufller 43 can be saved. The slitting chisel 20 of the present invention is shown in Figs. 1 and 3 as it would be used to remove the remaining fragment 47 of the exhaust pipe which surrounds the exterior of the stub 44. Thus, the pointed or sharpv p In addition; theY bladeI portions 26' and 27 have sharp tips oi p oirits, the blade ened tip of the blade portion 27 is inserted between the concentric tubular layers 47 and 44 and the blade portion is driven axially therebetween until the crotch 29 engages the axial end edge of the annular tail pipe fragment 47. When the cutting edge of the crotch 29 engages the annular fragment 47 the slitting action begins. As the portion 47 is slit longitudinally by the cutting edge 31, the chisel advances axially into the work and the generally concave outer surface of the blade portion 27 conforms to or fits against the curved exterior of the muffler stub 44, as seen in Fig. 3, to positionand guide the chisel. As the chisel advances, the taper 32 along the bottom of the channel 28 rolls the metal away from the cut and the outward wedging action of the blade 27 spreads the cut portion of the element 47 outwardly, as shown at 48 in Fig. 3. The outwardly extending blade portion 26 also assists in spreading and diverting the already slit portion 48, as also seen in Fig. 3. Because of the generally complementary coaction between the concave outer surface of the blade portion 27 and the exterior curvature of the tubular member 44, the latter is effectively protected from damage by gouging, scoring, or the like.

Referring now to Figs. 2 and 4, the use of the chisel in making an inside cut is also illustrated. In this instance, the straight cut has been made through the muier stub 44 at a point just beyond the end of the exhaust pipe 47 so that the tail pipe can be saved. In Fig. 2 the chisel 'is being used to remove the inner tubular fragment of the muflier stub 44. In this case, the tip of the blade 26 is inserted between the concentric tubular members 44 and 47 and the chisel is advanced axially until the cutting edge 31 at the crotch 29 engages the axial edge of the tubular element 44. Continued axial movement of the chisel causes a longitudinal slitting of the element 44 and during this slitting action the exterior convex curvature of the blade portion 26 conforms to and tits against the inner curved periphery of the element 47, as seen in Fig. 4, so as to position and guide the chisel. The rearward taper of the channel bottom 32 from the crotch 29 again causes the slit metal to be rolled away from the cut and the thickness of the blade portion 26 forces the slit metal inwardly away from the blade, as at 49 in Fig. 4. Likewise, the inwardly extending blade portion 27 assists in defiecting the slit metal portion 49 outwardly, as also seen in Fig. 4. In addition, the slitting is again accomplished without gouging, scoring or otherwise damaging the interior of the exhaust pipe 47 which is to be saved.

It will be appreciated that in actual use of the chisel, as described above, the oiset bend 24 in the shank of the chisel allows the chisel to enter the work in straight axial alignment therewith while the air hammer 40 is positioned out of alignment with the work but parallel thereto.

Although the invention has been described with reference to a specific structural embodiment thereof, it is to be understood that various modifications and equivalent structures may be resorted to without departing from the scope of the invention as defined in the appended claims.

We claim:

l. In a slitting chisel comprising an elongated metal body having a shank end and a cutting end, the improvement characterized in that said cutting end comprises an elongated channel portion which is generally V-shaped in transverse cross-section, the apex of the channel being rearwardly recessed at the outer end of said channel portion and providing an inwardly extending crotch with a sharp cutting edge, and the outer lateral surfaces of said channel portion having generally opposite curvatures, respectively, for fitting against either the interior or the exterior of a tubular member.

2. The structure of claim 1 further characterized in that the thickness of the metal along the apex of said channel increases rearwardly from said cutting edge to provide a rearwardly tapered bottoni in said channel.

3. In a slitting chisel comprising an elongated metal body having a shank end and a cutting end, the improvement characterized in that the cutting end comprises a pair of elongated angularly related blade portions forming a channel therebetween which is generally V-shaped in a plane transverse to the longitudinal axis of the chisel, the outermost end of each of said blade portions being smoothly tapered and the juncture between the tapered ends forming a rearwardly recessed crotch at the apex of said channel, said crotch having a sharp cutting edge, and the outer surfaces of said blade portions having generally concave and convex contours, respectively, in said plane.

4. The structure of claim 3 further characterized in that the tip of the blade portion having the convex outer contour is sharpened from both sides and the tip of the blade portion having the concave outer contour is sharpened from the inside surface only.

5. An improved cutting end structure for a slitting chisel or the like, comprising a pair of elongated blade portions having their outermost ends smoothly tapered along opposite longitudinal edges thereof, said blade portions being angularly connected to provide an elongated channel therebetween having a generally V-shaped cross section -in a plane transverse to the longitudinal axis of the chisel and the tapered innermost edges of said ends converging to form a rearwardly recessed crotch at the apex of said channel, said crotch having a sharp cutting edge, the outer surface of one of said blade portions having a generally convex curvature in said plane for cooperation with the interior curvature of a tubular member, and the outer surface of the other of said blade portions having a slightly concave curvature in said plane for cooperation with the exterior curvature of a tubular member.

References Cited in the file of this patent UNITED STATES PATENTS 1,276,458 Wagner Aug. 18, 1918 1,471,062 Riblett Oct. 16, 1923 1,598,458 Sullivan Aug. 3l, 1926 2,621,405 Facciuto Dec. 16, 1952 

